1. Field of the Invention
The present invention relates to an image measuring device capable of measuring a desired physical quantity based on a moving image captured by an imaging unit, an image measuring method capable of being executed by the image measuring device, and a computer program for causing a computer to execute a process of the image measuring method.
2. Description of Related Art
Conventionally, there have been developed image measuring devices which capture moving images of objects to be measured by imaging units, select target points of the captured moving images, and automatically track the target points so as to measure moving distances, speeds, acceleration, and the like of the target points. For example, Japanese Unexamined Patent Publication No. 2009-141709 discloses a moving image imaging apparatus for executing high-speed imaging for capturing instantaneously images as a continuous plurality of frame images whose imaging cycle is short so as to capture high-speed moving images.
In the moving image imaging apparatus disclosed in Japanese Unexamined Patent Publication No. 2009-141709, a position of a camera as an imaging unit is fixed, and a target point of a moving object to be measured is tracked by using frame images so as to be capable of measuring a moving distance, a speed, and acceleration of the target point.
However, when it is difficult to select a target point in such a case where a shape and an operation of an object to be measured are complicated, measurements cannot be carried out with sufficient accuracy by conventional image measuring methods. Further, it is occasionally difficult to determine whether a selected target point shows a desired motion of the object to be measured. In the conventional image measuring method, depending on shapes of objects to be measured, it is difficult to track target points by using frame images or the tracking cannot be performed. Therefore, a moving distance, a speed, and acceleration of a target point cannot be measured.
A plurality of frame images are still images at respective moments and thus it is difficult to correct a capturing position of an object to be measured that moves as time elapses. For this reason, a moving distance, a speed, and acceleration of the target point cannot be measured.
When calibration is performed, it is necessary to capture an object to be measured whose dimension is well known, such as a ruler, together with the object to be measured. However, when the shape of the object to be measured is complicated, the ruler cannot be always arranged in front of an imaging unit, and thus the dimension may fluctuate, whereby accurate calibration cannot be performed.